Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$206.72	13.829%	$235.3073	$235.31	$235.30	$235.30
Purchase #2	$161.78	11.576%	$180.5077	$180.51	$180.50	$180.50
Purchase #3	$214.68	7.855%	$231.5431	$231.54	$231.55	$231.50
Purchase #4	$103.51	4.699%	$108.3739	$108.37	$108.35	$108.40
Purchase #5	$218.96	6.670%	$233.5646	$233.56	$233.55	$233.60
Purchase #6	$9.29	10.468%	$10.2625	$10.26	$10.25	$10.30
Purchase #7	$101.96	10.756%	$112.9268	$112.93	$112.95	$112.90
7 purchase totals =	$1,016.90		$1,112.4859	$1,112.48	$1,112.45	$1,112.50